Testing Best Practices in Jest

// Good: Descriptive test names
test('should return user name when valid ID is provided', () => {})

// Good: Arrange-Act-Assert pattern
test('calculates total price with tax', () => {
  // Arrange
  const items = [{ price: 10 }, { price: 20 }]
  const taxRate = 0.1

  // Act
  const total = calculateTotal(items, taxRate)

  // Assert
  expect(total).toBe(33)
})

// Good: Test one thing at a time
test('validates email format', () => {
  expect(isValidEmail('test@example.com')).toBe(true)
})

test('rejects invalid email format', () => {
  expect(isValidEmail('invalid')).toBe(false)
})

// Good: Use beforeEach for setup
let service
beforeEach(() => {
  service = new UserService()
  jest.clearAllMocks()
})